1. Field of Invention
The present invention relates to radiography technology, in particular to a method for calibrating a dual-energy CT system and a corresponding image reconstruction method, which can eliminate a cupping artifact caused by X-ray beam hardening.
2. Description of Prior Art
As technology progresses, Computerized Tomography (CT) technique has been applied to systems for inspecting tourists' luggage. In the widely-used CT technique, an X-ray is utilized as a ray source which generates X-rays of continuous energy distribution. An image obtained by the conventional image reconstruction method represents the attenuation coefficient distribution of an object, which will give rise to a cupping artifact if affected by X-ray beam hardening.
In the existing algorithm of dual-energy CT image reconstruction, images of high- and low-energy attenuation coefficients for an object are first acquired using a conventional CT reconstruction method, and then calculation is made to obtain density and atomic number images. Such existing method cannot eliminate the cupping artifact due to hardening of rays and thus results in an inaccurate calculation result as well as reduced accuracy in material identification.